My experience with compiling ATAT 3.04 on a brand new Mac with Yosemite:
Compiler details (default g++ on the mac):
Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.0.0
Thread model: posix
Type
make
Two errors occur in arraylist.h lines 118 and 119 that the input pointer is not a class.
Go into arraylist.h and edit the lines such that "a.get_size()" now reads "a->get_size()".
So it seems like the compiler needs you to explicitly de-reference the pointer to the Array class.
After the changes to the header file type
make
Warnings can occur, ignore those. No errors should occur.
Then type
make install
as usual.
Hope this is useful.